Phil, check out the ticket I sent you when you have spare time.
Also I've seen a lot of facebook plugins going around on popular sites. e.g Ebuyer. I think you should implement one if you can.
View here as an example:
http://www.ebuyer.com/285944-fujitsu-ah531-laptop-vfy-ah531mrsc2gb
Product Discussion - Seems good to get conversations going, I know you have your smart comments but it saves customers signing in or typing there email address etc etc as nearly everyone is automatically logged into facebook these days.
http://developers.facebook.com/docs/plugins/
Also Social bookmarks module, you have one already but there isn't a Google +1 which would be helpful. I bought one from CMWebsite but it seemed to lag my site with twitter and the Google +1 not sure if it's been fixed yet.